/Engine/Plugins/Online/OnlineFramework/Source/Party/Public/SocialToolkit.h
Attempts to send a friend invite to another user based on display name or email. Only necessary to use this path when you do not have a knownUSocialUserfor this user already.
void TrySendFriendInvite ( const [FString](API\Runtime\Core\Containers\FString) & DisplayNameOrEmail ) const